Ring laser gyros use two counter-propagating beams of predetermined frequencies to measure the rotation rate about the sensitive axis of the ring as a function of the difference in frequency, i.e. the beat frequency, between the counter-propagating beams. The means normally used to produce such counter-propagating beams usually comprises an electric DC discharge in a gain medium, such as a suitable mixture of Helium and Neon. The electrical discharge gives rise to the so-called wall effect first explained by Langmuir. The discharge results in a negatively charged wall region which attracts positive neon ions but repels electrons. This causes an unbalanced electron pressure in that region which gives rise to a net force on the atoms of the gain medium which, in turn, drives a gas flow, customarily called Langmuir flow. Thus, in all presently known laser gyros, the gain medium is subject to a corresponding Langmuir flow. The interaction of the beams with the moving medium, normally referred to as the Fresnel-Fizeau drag, gives rise to a frequency shift of the counter-propagating beams, since the beam propagating in the direction of the flow sees an optical length which is different from that of the beam propagating in the direction opposite that of the flow. The flow then gives rise to a beat frequency between the counter-propagating beams which is not due to the rotation of the ring path, thus the output signal has a component which is normally referred to as the Fresnel-Fizeau bias. Present gyro configurations use two balanced electrical discharges in the two opposite directions in order to cancel the Fresnel-Fizeau bias. The main problem is that if the two electrical discharges are not perfectly balanced or if the two discharge bores are not perfectly matched, there is still a net bias due to the unbalanced Fresnel-Fizeau drag.